The present invention relates to heat pump water heaters which are not new per se. The invention also relates to ventilation of modern heavily insulated and sealed buildings. Such residences require forced ventilation in all seasons of the year. In winter it is desirable to exhaust air from the house and replace it with fresh, heated air. In summer it is desirable to exhaust the air from the house and replace it with cooled, fresh, dehumidified air. It is desirable to dehumidify the basement in summer. In spring and fall the stale air should be exhausted from the house and replaced with fresh outside air which is warmed up to a comfortable level. All of the desireable ventilation characteristics have been recognized but, if accommodated in a home, have entailed additional equipment and operating costs.
This invention is directed to operation of a heat pump water heater with a special ducting arrangement enabling all of the above characteristics to be achieved with the normal operation of the heat pump water heater. Initial testing indicates that the water heating cost with this system is competitive with natural gas (and about 50% of the cost of electric resistance heating) while giving the benefit of "free" dehumidification and ventilation. Furthermore, during the summer the system reduces the air conditioning requirements.